Move the passphraseRetriever to its own file.

Signed-off-by: Hu Keping <hukeping@huawei.com>

cmd/notary-signer/config.go

@@ -1,3 +1,16 @@
 package main
 
-import ()
+import (
+	"errors"
+	"strings"
+)
+
+func passphraseRetriever(keyName, alias string, createNew bool, attempts int) (passphrase string, giveup bool, err error) {
+	passphrase = mainViper.GetString(strings.ToUpper(alias))
+
+	if passphrase == "" {
+		return "", false, errors.New("expected env variable to not be empty: " + alias)
+	}
+
+	return passphrase, false, nil
+}

cmd/notary-signer/main.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"crypto/tls"
-	"errors"
 	_ "expvar"
 	"flag"
 	"fmt"
@@ -10,7 +9,6 @@ import (
 	"net"
 	"net/http"
 	"os"
-	"strings"
 	"time"
 
 	"google.golang.org/grpc"
@@ -66,16 +64,6 @@ func init() {
 	}
 }
 
-func passphraseRetriever(keyName, alias string, createNew bool, attempts int) (passphrase string, giveup bool, err error) {
-	passphrase = mainViper.GetString(strings.ToUpper(alias))
-
-	if passphrase == "" {
-		return "", false, errors.New("expected env variable to not be empty: " + alias)
-	}
-
-	return passphrase, false, nil
-}
-
 // Reads the configuration file for storage setup, and sets up the cryptoservice
 // mapping
 func setUpCryptoservices(configuration *viper.Viper, allowedBackends []string) (